Production of hydrocarbons from loose, unconsolidated, and/or fractured formations often produces large volumes of particulates along with the formation fluids. These particulates can cause a variety of problems. For this reason, operators use gravel packing as a common technique for controlling the production of such particulates.
To gravel pack a completion, a screen is lowered on a workstring into the wellbore and is placed adjacent the subterranean formation. Particulate material, collectively referred to as “gravel,” and a carrier fluid are pumped as a slurry down the workstring. Eventually, the slurry can exit through a “cross-over” into the wellbore annulus formed between the screen and the wellbore.
The carrier liquid in the slurry normally flows into the formation and/or through the screen itself. However, the screen is sized to prevent the gravel from flowing through the screen. This results in the gravel being deposited or “screened out” in the annulus between the screen and the wellbore to form a gravel-pack around the screen. The gravel, in turn, is sized so that it forms a permeable mass that allows produced fluids to flow through the mass and into the screen but blocks the flow of particulates into the screen.
Due to poor distribution, it is often difficult to completely pack the entire length of the wellbore annulus around the screen so that an interval in the annulus is not completely gravel packed. This poor distribution of gravel is often caused by the carrier liquid in the slurry being lost to the more permeable portions of the formation. Due to the loss of the carrier liquid, the gravel in the slurry forms “sand bridges” in the annulus before all of the gravel has been placed around the screen. Such bridges block further flow of the slurry through the annulus, thereby preventing the placement of sufficient gravel below the bridge in top-to-bottom packing operations or above the bridge in bottom-to-top packing operations.
Alternate flow conduits, called shunt tubes, can alleviate this bridging problem by providing a flow path for the slurry around such sand bridges. The shunt tubes are typically run along the length of the wellscreen and are attached to the screen by welds. Once the screen assemblies are joined, fluid continuity between the shunt tubes on adjacent screen assemblies must be provided, and several techniques have been developed to provide such continuity.
FIGS. 1A-1B are schematic views of examples of sand screens 18a-b provided with shunt tubes 30a-b in a wellscreen assembly 10. FIG. 2A illustrates an exploded view of the components for the wellscreen assembly 10 for use in an open hole. As an alternative, FIG. 2B illustrates an exploded view of components for the wellscreen assembly 10 for use in a cased hole.
In the assembly 10, a first sand control device 12a is coupled to a second sand control device 12b, and each device 12a-b has basepipe joints 14 joined together to define a production bore 16. Screens 18a-b having filter media surround the basepipe joints 14 and are supported by ribs 19. The assembly 10 is provided with shunt tubes 30a-b, which in this example are steel tubes having substantially rectangular cross-section. The shunt tubes 30a-b are supported on the exterior of the screens 18a-b and provide an alternate flow path 32 to the main production bore 16.
To provide fluid communication between the adjacent sand control devices 12a-b, jumper tubes 40 are disposed between the shunt tubes 30a-b. In this way, the shunt tubes 30a-b and the jumper tubes 40 maintain the flow path 32 outside the length of the assembly 10, even if the borehole's annular space B is bridged, for example, by a loss of integrity in a part of the formation F.
Additional examples of shunt tube arrangements can be found in U.S. Pat. Nos. 4,945,991 and 5,113,935. The shunt tubes may also be internal to the filter media, as described in U.S. Pat. Nos. 5,515,915 and 6,227,303.
As shown in FIGS. 1A-1B and 2A, the assembly for an open hole completion typically has main shrouds 28a-b that extend completely over the sand control devices 12a-b and provides a protective sleeve for the filter media and shunt tubes 30a-b. The shrouds 28a-b have apertures to allow for fluid flow. The main shrouds 28a-b terminate at the end rings 20a-b, which supports an end of the shroud 28a-b and have passages for the ends of the shunt tubes 30a-b. For a cased hole completion, the assembly 10 as shown in FIG. 2B may lack a shroud.
Either way, the shunt tubes 30a-b stop a certain length from the ends of the sand control devices 12a-b to allow handling room when the devices 12a-b are joined together at the rig. Once the devices 12a-b are joined, their respective shunt tubes 30a-b are linearly aligned, but there is a gap between them. Continuity of the shunt tubes' flow path 32 is typically established by installing the short, pre-sized jumper tubes 40 in the gap.
Each jumper tube 40 has a connector 50 at each end that contains a set of seals and is designed to slide onto the end of the jumper tube 40 in a telescoping engagement. When the jumper tube 40 is installed into the gap between the shunt tubes 30a-b, the connector 50 is driven partially off the end of the jumper tube 40 and onto the end of the shunt tube 30a-b until the connector 50 is in a sealing engagement with both shunt tubes 30a-b and the jumper tube 40. The shunt tubes' flow path 32 is established once both connectors 50 are in place. A series of set screws (not shown) can engage both the jumper tube 40 and adjoining shunt tube 30a-b. The screws are driven against the tube surfaces, providing a friction lock to secure the connector 50 in place.
This connection is not very secure, and there is concern that debris or protruding surfaces of the wellbore can dislodge the connectors 50 from sealing engagement with the tubes 30a-b and 40 while running the wellscreen assembly 10 into the wellbore. Therefore, a device called a split cover 22 as shown in FIG. 1A is typically used to protect the connectors 50. The split cover 22 is a piece of thin-gauge perforated tube, essentially the same diameter as the screen assembly 10, and the same length as the gap covered by the jumper tubes 40. The perforated cover 22 is spit into halves with longitudinal cuts, and the halves are rejoined with hinges along one seam and locking nut and bolt arrangements along the other seam. The split cover 22 can be opened, wrapped around the gap area between the sand control devices 12a-b, and then closed and secured with the locking bolts.
Other ways of connecting shunt tubes on adjoining sand control devices are known in the art. For example, U.S. Pat. No. 6,409,219 to Broome et al. describes a system wherein shunts on adjacent sand control devices are aligned when the correct torque is applied to join the devices. Alignment marks are included on the devices to indicate when the correct torque has been applied.
U.S. Pat. No. 5,341,880 to Thorstensen et al. describes a sand screen structure assembled from a plurality of generally tubular filter sections that are axially snapped together in a manner facilitating the simultaneous interconnection of circumferentially spaced series of axially extending shunt tubes secured to and passing internally through each of the filter sections. In an alternate embodiment of the sand screen structure, the shunt tubes are secured within external side surface recesses of the filter section bodies.
U.S. Pat. No. 5,868,200 to Bryant et al. describes an alternate-path wellscreen that is made-up of joints. The screen has a sleeve positioned between the ends of adjacent joints. The sleeve acts as a manifold for fluidly-connecting the alternate-paths on one joint with the alternate-paths on an adjacent joint.
Another connector is disclosed in U.S. Pat. No. 7,497,267, which is incorporated herein by reference. FIGS. 3A-3B show examples of connections 100a-b disclosed therein. The connections 100a-b secure a jumper tube 40 to a shunt tube 30. In general, the connections 100a-b are designed to slide onto the end of the jumper tube 40 in a telescoping engagement. When the jumper tube 40 is installed into the gap between the shunt tubes 30, the connections 100a-b are driven partially off of the end of the jumper tube 40 and onto the end of the shunt tube 30 to form a sealing engagement between both tubes 30 and 40. Lugs and set screws are then used to secure the connectors 100a-b in place.
For example, FIG. 3A shows a connection 100a having a connector 108 and a connector lock 102 disposed on a jumper tube 40. The jumper tube 40 has lugs 104 affixed to its sides. The connector 108 is pushed forward to engage a shunt tube 30 secured to the end ring 20. The connector lock 102 is the secured in place by screwing the screws 106 in the lock 102 to keep the lugs 104 in the side slots in the lock 102. The lugs 104 and screws 106 secure the lock 102 in the position to hold the connector 108 in the engaged position. As also shown in FIG. 3A, the connector 108 can include a sealing ring 109 to contact the shunt tube 30.
In another example, FIG. 3B shows a connection 100b having a connector 110 disposed on a jumper tube 40. A “C”-shaped receiver 112 is affixed to the shunt tube 30 and is positioned with the open side of the “C” toward the end of the tube 30. The connector 110 is moved to engage the shunt tube 30 so that the end of the connector 110 fits in the receiver 112. The connector 110 is attached to the jumper tube 40 with set screws 116, and other set screws 114 on the receiver 112 align with mating holes (not apparent in this view) in connector 110 to affix the tubes 30 and 40 together.
Although the above-techniques for connecting shunt tubes on adjoining joints of a wellscreen assembly may be effective, operators seek more efficient and reliable ways to make these connections at the rig during deployment of the assembly. The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.